A conventional radio communication system 1 is comprised of a server 2 and a portable radio terminal 7 as shown in FIG. 8, and a streaming data D3 is transmitted from the server 2 to the portable radio terminal 7 through a communication channel 6.
That is, the server 2 inputs contents data D1 to an encoding division 3 at first. The encoding division 3 performs compression coding of the contents data D1 with the stated compression coding system, and once stores the resulted coded data D2 in the data storing division 4, and then supplies this to the data outputting division 5.
The data outputting division 5 adds error correcting code to the coded data D2, transforms it into packets, modulates it in accordance with the stated modulating system, generates the streaming data D3 hereby, and transmits this to the portable radio terminal 7 via the communication channel 6.
As to the communication channel 6, the streaming data D3 is sent to a base station (not shown) with a wired system, while it is sent from the base station to the portable radio terminal 7 with a wireless system, so it is variously influenced by changes of the transmission situation in the wireless section.
The portable radio terminal 7 receives the streaming data D3 by means of the data receiving division 8, applies demodulation processing and error correction processing to it, obtains the demodulated data D4 hereby, and once stores this in the data storing division 9, and then sends this to a decoding division 10.
The decoding division 10 decodes the demodulated data D4, sends the resulted decoded data D5 to the displaying division 11, and displays the contents of the contents via the displaying division 11, and allows the user to view and listen to it hereby.
By the way, in the radio communication system 1 having such a construction, in the case where the transmission speed (shown with a broken line) on the communication channel 6 varies every moment in t1 section, t2 section, t3 section, t4 section, and the following sections (not shown) as shown in FIG. 9(A), while the streaming data D3 is sent from the server 2 to the portable radio terminal 7 at the transmission speed of 128 [kbps] as shown in FIG. 9(B), it is not able to send whole data of A2 portion and C2 portion (shown with a X mark) out of the streaming data D3, because the transmission speed on the communication channel 6 changes in practice as shown in FIG. 9(C).
In this case, it is not able to exactly apply error correction processing to the data of A2 portion and C2 portion out of the streaming data D3 with the data receiving division 8 of the portable radio terminal 7, and, as a result, the data itself of A2 portion and C2 portion is missed.
So, in order to avoid such missing of data, in the radio communication system 1, in the case where the instantaneous real transmission speed in the communication channel 6 varies every moment in t1 section-t4 section as shown in FIG. 10(A), which has the same contents as that of FIG. 9(A), in the case where the streaming data D3 has been transmitted from the server 2 at the transmission speed of 64 [kbps], which is the minimum value of the transmission speed, as shown in FIG. 10(B), the portable radio terminal 7 is able to receive the whole data without missing though the quantity of data transmission becomes the half of that of the transmission speed of 128 [kbps], as shown in FIG. 12(C).
However, in this case, though it is originally able to transmit at the transmission speed of 128 [kbps] without missing with respect to t2 section and t4 section, it transmits at the transmission speed of only 64 [kbps], so the communication capacity in the communication channel 6 can not be utilized effectively.
Thus, as to the radio communication system 1, in the case where the streaming data D3 is sent at the transmission speed of 128 [kbps], A2 portion and C2 portion out of the streaming data D3 that are to be received by the portable radio terminal 7 of the receiving side are missed; in the case where the streaming data D3 is sent at the transmission speed of 64 [kbps], whole data can be received with the portable radio terminal 7, however, the quantity of the data becomes about the half; thus, there has been such a problem that the communication throughput is poor anyway.